U.S. patent number 8,969,221 [Application Number 11/725,525] was granted by the patent office on 2015-03-03 for inhibition of water penetration into ballistic materials.
This patent grant is currently assigned to Honeywell International Inc. The grantee listed for this patent is Henry G. Ardiff, Brian D. Arvidson, Ashok Bhatnagar, David A. Hurst, Lori L. Wagner. Invention is credited to Henry G. Ardiff, Brian D. Arvidson, Ashok Bhatnagar, David A. Hurst, Lori L. Wagner.
United States Patent |
8,969,221 |
Arvidson , et al. |
March 3, 2015 |
Inhibition of water penetration into ballistic materials
Abstract
Ballistic resistant articles having excellent resistance to
deterioration due to liquid exposure. More particularly, ballistic
resistant fibrous composites and articles that retain their
superior ballistic resistance performance after exposure to liquids
such as sea water and organic solvents, such as gasoline and other
petroleum-based products.
Inventors: |
Arvidson; Brian D. (Chester,
VA), Hurst; David A. (Richmond, VA), Wagner; Lori L.
(Richmond, VA), Bhatnagar; Ashok (Richmond, VA), Ardiff;
Henry G. (Chesterfield, VA) |
Applicant: |
Name |
City |
State |
Country |
Type |
Arvidson; Brian D.
Hurst; David A.
Wagner; Lori L.
Bhatnagar; Ashok
Ardiff; Henry G. |
Chester
Richmond
Richmond
Richmond
Chesterfield |
VA
VA
VA
VA
VA |
US
US
US
US
US |
|
|
Assignee: |
Honeywell International Inc
(Morristown, NJ)
|
Family
ID: |
39677736 |
Appl.
No.: |
11/725,525 |
Filed: |
March 19, 2007 |
Prior Publication Data
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|
|
|
Document
Identifier |
Publication Date |
|
US 20130115839 A1 |
May 9, 2013 |
|
Current U.S.
Class: |
442/135; 156/60;
89/939; 428/911; 428/912; 89/901 |
Current CPC
Class: |
B32B
5/26 (20130101); F41H 5/0478 (20130101); B32B
27/08 (20130101); B32B 27/12 (20130101); B32B
5/12 (20130101); Y10S 428/911 (20130101); Y10T
442/20 (20150401); Y10S 428/912 (20130101); Y10T
442/2861 (20150401); Y10T 442/2893 (20150401); Y10T
156/10 (20150115); Y10T 442/2877 (20150401); Y10T
442/2623 (20150401); Y10T 442/2885 (20150401); Y10T
442/291 (20150401) |
Current International
Class: |
B32B
27/12 (20060101); F41H 5/08 (20060101); B64D
37/06 (20060101); B29C 65/00 (20060101) |
Field of
Search: |
;428/911-912
;442/134-135 ;89/901-939 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2004530039 |
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Sep 2004 |
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JP |
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02/101319 |
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Dec 2002 |
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WO |
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2007003334 |
|
Jan 2007 |
|
WO |
|
Other References
http://www.bayermaterialsciencenafta.com/products/index.cfm?mode=grades&pp-
.sub.--num=EB7C4BD9-0DCD-BBE0-A4B3F13F669BA736&o.sub.--num=13;
Aug. 27, 2006. cited by examiner .
Bayhydrol 124 Technical Data Sheet, Aug. 27, 2006. cited by
examiner.
|
Primary Examiner: Pierce; Jeremy R.
Assistant Examiner: Lopez; Ricardo E
Claims
What is claimed is:
1. A fibrous composite material, comprising in order: a) a first
outer polymer film; b) a first fibrous layer in contact with the
first outer polymer film; the first fibrous layer comprising a
plurality of fibers wherein said fibers are impregnated with a
polymeric binder material that is resistant to dissolution by water
and resistant to dissolution by gasoline; c) a central polymer film
in contact with the first fibrous layer; d) a second fibrous layer
in contact with the central polymer film; the second fibrous layer
comprising a plurality of fibers wherein said fibers are
impregnated with a polymeric binder material that is resistant to
dissolution by water and resistant to dissolution by gasoline; and
e) a second outer polymer film in contact with the second fibrous
layer; wherein the first fibrous layer and the second fibrous layer
each comprise fibers having a tenacity of about 7 g/denier or more
and a tensile modulus of about 150 g/denier or more, wherein said
polymeric binder material encapsulates each of the fibers such that
100% of the fiber surface area is covered with said binder
material.
2. The fibrous composite material of claim 1 wherein the first
fibrous layer and the second fibrous layer each comprise a single
ply of non-woven, non-overlapping fibers that are aligned in a
substantially parallel array.
3. The fibrous composite material of claim 2 wherein the parallel
fibers of said first fibrous layer are positioned orthogonally to
the parallel fibers of said second fibrous layer, relative to the
longitudinal fiber direction of each fiber ply.
4. The fibrous composite material of claim 1 wherein the first
fibrous layer and the second fibrous layer each comprise a
plurality of consolidated non-woven fiber plies.
5. The fibrous composite material of claim 1 wherein the first
fibrous layer and the second fibrous layer each comprise a
plurality of overlapping non-woven fiber plies that are
consolidated into a single element, wherein each ply comprises
fibers aligned in a substantially parallel array and wherein each
ply of a fibrous layer is positioned orthogonally to the parallel
fibers of each adjacent ply within that fibrous layer relative to
the longitudinal fiber direction of each fiber ply.
6. The fibrous composite material of claim 1 wherein the first
fibrous layer and the second fibrous layer each consist of fibers
that are impregnated with a polymeric binder material.
7. The fibrous composite material of claim 1 wherein said fibers of
each fibrous layer comprise polyolefin fibers, aramid fibers,
polybenzazole fibers, polyvinyl alcohol fibers, polyamide fibers,
polyethylene terephthalate fibers, polyethylene naphthalate fibers,
polyacrylonitrile fibers, liquid crystal copolyester fibers, rigid
rod fibers comprising
pyridobisimidazole-2,6-diyl(2,5-dihydroxy-p-phenylene), or a
combination thereof.
8. The fibrous composite material of claim 1 wherein said polymeric
binder material that is resistant to dissolution by water and
resistant to dissolution by gasoline comprises a hydrolytically
stable, polar polymer.
9. The fibrous composite material of claim 1 wherein said polymeric
binder material that is resistant to dissolution by water and
resistant to dissolution by gasoline comprises a polar, vinyl-based
polymer.
10. The fibrous composite material of claim 1 wherein said
polymeric binder material that is resistant to dissolution by water
and resistant to dissolution by gasoline comprises a non-polar
polymer modified with polar groups.
11. The fibrous composite material of claim 1 wherein said
polymeric binder material that is resistant to dissolution by water
and resistant to dissolution gasoline comprises a polar,
hydrolytically stable thermoplastic polyurethane.
12. The fibrous composite material of claim 1 wherein said first
outer polymer film, said central polymer film and said second outer
polymer film comprise polyolefins, polyamides, polyesters,
polyurethanes, vinyl polymers, fluoropolymers, or copolymers or
combinations thereof.
13. The fibrous composite material of claim 1 wherein said first
outer polymer film, said central polymer film and said second outer
polymer film each comprise linear low density polyethylene.
14. The fibrous composite material of claim 1 wherein said
polymeric binder material comprises from about 3% to about 16% by
weight of each the first fibrous layer and the second fibrous
layer.
15. A ballistic resistant article formed from the fibrous composite
material of claim 1.
16. A method of forming a fibrous composite material, comprising:
a) providing a first outer polymer film; b) attaching a first
fibrous layer to the first outer polymer film; the first fibrous
layer comprising a plurality of fibers wherein said fibers are
impregnated with a polymeric binder material that is resistant to
dissolution by water and resistant to dissolution by gasoline; c)
attaching a central polymer film to the first fibrous layer; d)
attaching a second fibrous layer to the central polymer film; the
second fibrous layer comprising a plurality of fibers wherein said
fibers are impregnated with a polymeric binder material that is
resistant to dissolution by water and resistant to dissolution by
gasoline; and e) attaching a second outer polymer film to the
second fibrous layer; wherein the first fibrous layer and the
second fibrous layer each comprise fibers having a tenacity of
about 7 g/denier or more and a tensile modulus of about 150
g/denier or more, wherein said polymeric binder material
encapsulates each of the fibers such that 100% of the fiber surface
area is covered with said binder material.
17. The method of claim 16 wherein the first fibrous layer and the
second fibrous layer each comprise a single ply of non-woven,
non-overlapping fibers that are aligned in a substantially parallel
array.
18. The method of claim 17 wherein the parallel fibers of said
first fibrous layer are positioned orthogonally to the parallel
fibers of said second fibrous layer, relative to the longitudinal
fiber direction of each fiber ply.
19. The method of claim 16 wherein the first fibrous layer and the
second fibrous layer each comprise a plurality of consolidated
non-woven fiber plies.
20. The method of claim 16 wherein the first fibrous layer and the
second fibrous layer each comprise a plurality of overlapping
non-woven fiber plies that are consolidated into a single element,
wherein each ply comprises fibers aligned in a substantially
parallel array and wherein each ply of a fibrous layer is
positioned orthogonally to the parallel fibers of each adjacent ply
within that fibrous layer relative to the longitudinal fiber
direction of each fiber ply.
21. The method of claim 16 wherein the first fibrous layer and the
second fibrous layer each comprise a woven array of fibers.
22. The method of claim 16 wherein said polymeric binder material
that is resistant to dissolution by water and resistant to
dissolution by gasoline comprises a polar, vinyl-based polymer.
23. The method of claim 16 wherein said polymeric binder material
that is resistant to dissolution by water and resistant to
dissolution by gasoline comprises a polar, hydrolytically stable
thermoplastic polyurethane, which polyurethane has been modified
with polar groups.
24. The method of claim 16 wherein said first outer polymer film,
said central polymer film and said second outer polymer film
comprise polyolefins, polyamides, polyesters, polyurethanes, vinyl
polymers, fluoropolymers, or copolymers or combinations
thereof.
25. The method of claim 16 wherein said polymeric binder material
comprises a hydrolytically stable, polar polymer or comprises a
non-polar polymer modified with polar groups.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to ballistic resistant articles having
excellent resistance to deterioration due to liquid exposure. More
particularly, the invention pertains to ballistic resistant fabrics
and articles that retain their superior ballistic resistance
performance after exposure to liquids such as sea water and organic
solvents, such as gasoline and other petroleum-based products.
2. Description of the Related Art
Ballistic resistant articles containing high strength fibers that
have excellent properties against projectiles are well known.
Articles such as bullet resistant vests, helmets, vehicle panels
and structural members of military equipment are typically made
from fabrics comprising high strength fibers. High strength fibers
conventionally used include polyethylene fibers, aramid fibers such
as poly(phenylenediamine terephthalamide), graphite fibers, nylon
fibers, glass fibers and the like. For many applications, such as
vests or parts of vests, the fibers may be used in a woven or
knitted fabric. For other applications, the fibers may be
encapsulated or embedded in a matrix material to form woven or
non-woven rigid or flexible fabrics.
Various ballistic resistant constructions are known that are useful
for the formation of hard or soft armor articles such as helmets,
panels and vests. For example, U.S. Pat. Nos. 4,403,012, 4,457,985,
4,613,535, 4,623,574, 4,650,710, 4,737,402, 4,748,064, 5,552,208,
5,587,230, 6,642,159, 6,841,492, 6,846,758, all of which are
incorporated herein by reference, describe ballistic resistant
composites which include high strength fibers made from materials
such as extended chain ultra-high molecular weight polyethylene.
These composites display varying degrees of resistance to
penetration by high speed impact from projectiles such as bullets,
shells, shrapnel and the like.
For example, U.S. Pat. Nos. 4,623,574 and 4,748,064 disclose simple
composite structures comprising high strength fibers embedded in an
elastomeric matrix. U.S. Pat. No. 4,650,710 discloses a flexible
article of manufacture comprising a plurality of flexible layers
comprised of high strength, extended chain polyolefin (ECP) fibers.
The fibers of the network are coated with a low modulus elastomeric
material. U.S. Pat. Nos. 5,552,208 and 5,587,230 disclose an
article and method for making an article comprising at least one
network of high strength fibers and a matrix material that includes
a vinyl ester and diallyl phthalate. U.S. Pat. No. 6,642,159
discloses an impact resistant rigid composite having a plurality of
fibrous layers which comprise a network of filaments disposed in a
matrix, with elastomeric layers there between. The composite is
bonded to a hard plate to increase protection against armor
piercing projectiles.
Hard or rigid body armor provides good ballistic resistance, but
can be very stiff and bulky. Accordingly, body armor garments, such
as ballistic resistant vests, are preferably formed from flexible
or soft armor materials. However, while such flexible or soft
materials exhibit excellent ballistic resistance properties, they
also generally exhibit poor resistance to liquids, including fresh
water, seawater and organic solvents, such as petroleum, gasoline,
gun lube and other solvents derived from petroleum. This is
problematic because the ballistic resistance performance of such
materials is generally known to deteriorate when exposed to or
submerged in liquids. Further, while it has been known to apply a
protective film to a fabric surface to enhance fabric durability
and abrasion resistance, as well as water or chemical resistance,
these films add weight to the fabric. Accordingly, it would be
desirable in the art to provide soft, flexible ballistic resistant
materials that perform at acceptable ballistic resistance standards
after being contacted with or submerged in a variety of liquids,
and also have superior durability.
The present invention provides fibrous composite materials that
offers the desired protection from liquids, as well as heat and
cold resistance, and resistance to abrasion and wear, while
maintaining good flexibility. Particularly, the invention provides
ballistic resistant structures incorporating at least two fibrous
layers that are surrounded on each of their surfaces by a polymer
film, and wherein fibrous layers comprise fibers that are at least
partially coated with a polymeric binder material that is resistant
to dissolution by water and resistant to dissolution by one or more
organic solvents. It has been discovered that this combination of
polymer films with the fibrous layers contribute to the retention
of the ballistic resistance properties of a fabric after prolonged
exposure to potentially harmful liquids, eliminating the need for a
protective surface film to achieve such benefits. It has also been
unexpectedly found that the presence of polymer films on each fiber
surface inhibits the wicking of liquids into the fabric at the
fabric edges and prevents liquids from settling into spaces between
fibers. Accordingly, the fabrics of the invention retain a low
weight after being submerged in water or other liquids.
SUMMARY OF THE INVENTION
The invention provides a fibrous composite material, comprising in
order:
a) a first outer polymer film;
b) a first fibrous layer in contact with the first outer polymer
film; the first fibrous layer comprising a plurality of fibers
wherein said fibers are at least partially coated with a polymeric
binder material that is resistant to dissolution by water and
resistant to dissolution by one or more organic solvents;
c) a central polymer film in contact with the first fibrous
layer;
d) a second fibrous layer in contact with the central polymer film;
the second fibrous layer comprising a plurality of fibers wherein
said fibers are at least partially coated with a polymeric binder
material that is resistant to dissolution by water and resistant to
dissolution by one or more organic solvents; and
e) a second outer polymer film in contact with the second fibrous
layer.
The invention also provides a method of forming a fibrous composite
material, comprising:
a) providing a first outer polymer film;
b) attaching a first fibrous layer to the first outer polymer film;
the first fibrous layer comprising a plurality of fibers wherein
said fibers are at least partially coated with a polymeric binder
material that is resistant to dissolution by water and resistant to
dissolution by one or more organic solvents;
c) attaching a central polymer film to the first fibrous layer;
d) attaching a second fibrous layer to the central polymer film;
the second fibrous layer comprising a plurality of fibers wherein
said fibers are at least partially coated with a polymeric binder
material that is resistant to dissolution by water and resistant to
dissolution by one or more organic solvents; and
e) attaching a second outer polymer film to the second fibrous
layer.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic representation of a five-layer composite
structure of the invention wherein each of the first and second
fibrous layers are made up of a unidirectional non-woven parallel
array.
FIG. 2 is a schematic representation of a five-layer composite
structure of the invention wherein each of the first and second
fibrous layers are made up of multiple layers of overlapping
non-woven fiber plies or alternatively woven fabrics.
DETAILED DESCRIPTION OF THE INVENTION
The invention presents a fibrous composite material and articles
that retain superior ballistic penetration resistance after
exposure to water, particularly sea water, and organic solvents,
particularly solvents derived from petroleum such as gasoline. The
articles of the invention have superior ballistic penetration
resistance against high energy ballistic threats, including bullets
and high energy fragments, such as shrapnel.
The fibrous composite material of the invention is characterized by
alternating polymer films and fibrous layers, where each adjacent
layer of the material is different. FIGS. 1 and 2 schematically
illustrate the preferred layering structures of the composites of
the invention. As illustrated in FIGS. 1 and 2, the fibrous
composite material of the invention preferably comprises one of two
preferred structures. Each structure preferably includes at least
five component layers. Additional alternating layers may be
included, although five total layers is most preferred to maintain
a low weight. As shown in FIG. 1, a fibrous composite material 10
is illustrated comprising, in order, a first outer polymer film 14,
a first fibrous layer 20, a central polymer film 16, a second
fibrous layer 22 and a second outer polymer film 18. As shown in
FIG. 2, a fibrous composite material 12 is illustrated comprising,
in order, a first outer polymer film 14, a first fibrous layer 24,
a central polymer film 16, a second fibrous layer 26 and a second
outer polymer film 18.
Each embodiment includes multiple polymer films and multiple
fibrous layers. The two embodiments differ primarily in the
structure of the fibrous layers. In the first embodiment of the
invention, illustrated in FIG. 1, first fibrous layer 20 and second
fibrous layer 22 each comprise a single ply of non-woven,
preferably non-overlapping fibers that are aligned in a
unidirectional, substantially parallel array. This type of fibrous
layer is known in the art as a "unitape" (or "unidirectional tape")
and is also referred to herein as a "single ply". As illustrated in
the figure, the parallel fibers of said first fibrous layer 20 are
preferably positioned orthogonally to the parallel fibers of said
second fibrous layer 22, relative to the longitudinal fiber
direction of each fiber ply, such that the fibers of each fibrous
layer are cross-plied at 0.degree./90.degree. with respect to each
other. As is conventionally known in the art, excellent ballistic
resistance is achieved when individual fiber layers are cross-plied
such that the fiber alignment direction of one layer is rotated at
an angle with respect to the fiber alignment direction of another
layer. Adjacent layers can be aligned at virtually any angle
between about 0.degree. and about 90.degree. with respect to the
longitudinal fiber direction of another layer. Most preferably, the
fibers of fibrous layer 20 and fibrous layer 22 are cross-plied
orthogonally at 0.degree. and 90.degree. angles.
In accordance with the invention, each single ply fibrous layer of
this first embodiment comprises fibers that are at least partially
coated with a polymeric binder material that is resistant to
dissolution by water and resistant to dissolution by one or more
organic solvents. This polymeric binder material assists in the
merging of layers 14, 16, 18, 24 and 26, as well as in providing a
stable composite material having good resistance to degradation due
to environmental contaminants.
In the second embodiment of the invention, first fibrous layer 24
and second fibrous layer 26 each preferably comprise a plurality of
overlapping non-woven fiber plies that are consolidated into a
single-layer, monolithic element, wherein each ply comprises fibers
aligned in a unidirectional, substantially parallel array and
wherein each ply of a fibrous layer is positioned orthogonally to
the parallel fibers of each adjacent ply within that fibrous layer
relative to the longitudinal fiber direction of each fiber ply
(unitape). Each of fibrous layers 24 and 26 also comprise fibers
that are at least partially coated with a polymeric binder material
that is resistant to dissolution by water and resistant to
dissolution by one or more organic solvents. Most preferably
fibrous layers 24 and 26 include only two consolidated "unitapes"
cross-plied at 0.degree./90.degree., but additional unitapes may be
incorporated within the consolidated single-layer element, and
adjacent plies may also be cross-plied at angles other than
0.degree. and 90.degree.. Any additional layers are also preferably
cross-plied at an angle relative to the longitudinal fiber
direction of adjacent fiber plies. For example, a five layer
non-woven structure may have plies at a
0.degree./45.degree./90.degree./45.degree./0.degree. orientation or
at other angles. Such rotated unidirectional alignments are
described, for example, in U.S. Pat. Nos. 4,457,985; 4,748,064;
4,916,000; 4,403,012; 4,623,573; and 4,737,402. Most typically,
fibrous layers 24 and 26, when comprising non-woven fiber plies,
will include from 1 to about 6 plies, but may include as many as
about 10 to about 20 plies as may be desired for various
applications. Such non-woven fibrous layers may be constructed
using well known methods, such as by the methods described in U.S.
Pat. No. 6,642,159.
The greater the number of plies translates into greater ballistic
resistance, but also greater weight. The number of fiber plies
forming a fibrous layer 24 or 26, or forming a composite structure
10 where additional single-ply fibrous layers attached, varies
depending upon the ultimate use of the desired ballistic resistant
article. For example, in body armor vests for military
applications, in order to form an article composite that achieves a
desired 1.0 pound per square foot areal density (4.9 kg/m.sup.2), a
total of at 22 individual plies may be required, wherein the plies
may be woven, knitted, felted or non-woven fabrics formed from the
high-strength fibers described herein. In another embodiment, body
armor vests for law enforcement use may have a number of layers
based on the National Institute of Justice (NIJ) Threat Level. For
example, for an NIJ Threat Level IIIA vest, there may also be a
total of 22 layers. For a lower NIJ Threat Level, fewer layers may
be employed.
Fibrous layers 24 and 26 may alternately comprise woven fibrous
layers. Woven fibrous layers may be formed using techniques that
are well known in the art using any fabric weave, such as plain
weave, crowfoot weave, basket weave, satin weave, twill weave and
the like. Plain weave is most common, where fibers are woven
together in a 0.degree./90.degree. orientation. In another
embodiment, a hybrid structure may be assembled where one fibrous
layer comprises a woven fibrous layer and another fibrous layer
comprises a non-woven fibrous layer. Alternately, fibrous layers 24
and 26 may also comprise a consolidated combination of woven and
non-woven fiber plies.
For the purposes of the present invention, a "fiber" is an elongate
body the length dimension of which is much greater than the
transverse dimensions of width and thickness. The cross-sections of
fibers for use in this invention may vary widely. They may be
circular, flat or oblong in cross-section. Accordingly, the term
fiber includes filaments, ribbons, strips and the like having
regular or irregular cross-section. They may also be of irregular
or regular multi-lobal cross-section having one or more regular or
irregular lobes projecting from the linear or longitudinal axis of
the fibers. It is preferred that the fibers are single lobed and
have a substantially circular cross-section.
As used herein, an "array" describes an orderly arrangement of
fibers or yarns, and a "parallel array" describes an orderly
parallel arrangement of fibers or yarns. A fiber "layer" describes
a planar arrangement of woven or non-woven fibers or yarns. As used
herein, a "single-layer" structure refers to monolithic structure
composed of one or more individual fiber layers that have been
consolidated into a single unitary structure. In general, a
"fabric" may relate to either a woven or non-woven material. The
fibrous plies of the invention may alternately comprise yarns
rather than fibers, where a "yarn" is a strand consisting of
multiple filaments. Non-woven fibrous plies may also comprise
felted structures which are formed using conventionally known
techniques, comprising fibers in random orientation.
In accordance with the invention, the fibers comprising each of
fibrous layers 20, 22, 24 and 26 preferably comprise high-strength,
high tensile modulus fibers. As used herein, a "high-strength, high
tensile modulus fiber" is one which has a preferred tenacity of at
least about 7 g/denier or more, a preferred tensile modulus of at
least about 150 g/denier or more, and preferably an energy-to-break
of at least about 8 J/g or more, each both as measured by ASTM
D2256. As used herein, the term "denier" refers to the unit of
linear density, equal to the mass in grams per 9000 meters of fiber
or yarn. As used herein, the term "tenacity" refers to the tensile
stress expressed as force (grams) per unit linear density (denier)
of an unstressed specimen. The "initial modulus" of a fiber is the
property of a material representative of its resistance to
deformation. The term "tensile modulus" refers to the ratio of the
change in tenacity, expressed in grams-force per denier (g/d) to
the change in strain, expressed as a fraction of the original fiber
length (in/in).
Particularly suitable high-strength, high tensile modulus fiber
materials include polyolefin fibers, particularly extended chain
polyolefin fibers, such as highly oriented, high molecular weight
polyethylene fibers, particularly ultra-high molecular weight
polyethylene fibers and ultra-high molecular weight polypropylene
fibers. Also suitable are aramid fibers, particularly para-aramid
fibers, polyamide fibers, polyethylene terephthalate fibers,
polyethylene naphthalate fibers, extended chain polyvinyl alcohol
fibers, extended chain polyacrylonitrile fibers, polybenzazole
fibers, such as polybenzoxazole (PBO) and polybenzothiazole (PBT)
fibers, and liquid crystal copolyester fibers. Each of these fiber
types is conventionally known in the art.
In the case of polyethylene, preferred fibers are extended chain
polyethylenes having molecular weights of at least 500,000,
preferably at least one million and more preferably between two
million and five million. Such extended chain polyethylene (ECPE)
fibers may be grown in solution spinning processes such as
described in U.S. Pat. No. 4,137,394 or 4,356,138, which are
incorporated herein by reference, or may be spun from a solution to
form a gel structure, such as described in U.S. Pat. Nos. 4,551,296
and 5,006,390, which are also incorporated herein by reference. A
particularly preferred fiber type for use in the invention are
polyethylene fibers sold under the trademark SPECTRA.RTM. from
Honeywell International Inc. SPECTRA.RTM. fibers are well known in
the art and are described, for example, in U.S. Pat. Nos. 4,623,547
and 4,748,064.
Also particularly preferred are aramid (aromatic polyamide) or
para-aramid fibers. Such are commercially available and are
described, for example, in U.S. Pat. No. 3,671,542. For example,
useful poly(p-phenylene terephthalamide) filaments are produced
commercially by Dupont corporation under the trade name of
KEVLAR.RTM.. Also useful in the practice of this invention are
poly(m-phenylene isophthalamide) fibers produced commercially by
Dupont under the trade name NOMEX.RTM. and fibers produced
commercially by Teijin under the trade name TWARON.RTM..
Suitable polybenzazole fibers for the practice of this invention
are commercially available and are disclosed for example in U.S.
Pat. Nos. 5,286,833, 5,296,185, 5,356,584, 5,534,205 and 6,040,050,
each of which are incorporated herein by reference. Preferred
polybenzazole fibers are ZYLON.RTM. brand fibers from Toyobo Co.
Suitable liquid crystal copolyester fibers for the practice of this
invention are commercially available and are disclosed, for
example, in U.S. Pat. Nos. 3,975,487; 4,118,372 and 4,161,470, each
of which is incorporated herein by reference.
Suitable polypropylene fibers include highly oriented extended
chain polypropylene (ECPP) fibers as described in U.S. Pat. No.
4,413,110, which is incorporated herein by reference. Suitable
polyvinyl alcohol (PV-OH) fibers are described, for example, in
U.S. Pat. Nos. 4,440,711 and 4,599,267 which are incorporated
herein by reference. Suitable polyacrylonitrile (PAN) fibers are
disclosed, for example, in U.S. Pat. No. 4,535,027, which is
incorporated herein by reference. Each of these fiber types is
conventionally known and widely commercially available.
The other suitable fiber types for use in the present invention
include glass fibers, fibers formed from carbon, fibers formed from
basalt or other minerals, rigid rod fibers such as M5.RTM. fibers,
and combinations of all the above materials, all of which are
commercially available. For example, the fibrous layers may be
formed from a combination of SPECTRA.RTM. fibers and Kevlar.RTM.
fibers. M5.RTM. fibers are formed from
pyridobisimidazole-2,6-diyl(2,5-dihydroxy-p-phenylene) and are
available from Magellan Systems International of Richmond, Va. and
are described, for example, in U.S. Pat. Nos. 5,674,969, 5,939,553,
5,945,537, and 6,040,478, each of which is incorporated herein by
reference. Specifically preferred fibers include M5.RTM. fibers,
polyethylene SPECTRA.RTM. fibers, and aramid Kevlar.RTM. fibers.
The fibers may be of any suitable denier, such as, for example, 50
to about 3000 denier, more preferably from about 200 to 3000
denier, still more preferably from about 650 to about 2000 denier,
and most preferably from about 800 to about 1500 denier.
The most preferred fibers for the purposes of the invention are
either high-strength, high tensile modulus extended chain
polyethylene fibers or high-strength, high tensile modulus
para-aramid fibers. As stated above, a high-strength, high tensile
modulus fiber is one which has a preferred tenacity of about 7
g/denier or more, a preferred tensile modulus of about 150 g/denier
or more and a preferred energy-to-break of about 8 J/g or more,
each as measured by ASTM D2256. In the preferred embodiment of the
invention, the tenacity of the fibers should be about 15 g/denier
or more, preferably about 20 g/denier or more, more preferably
about 25 g/denier or more and most preferably about 30 g/denier or
more. The fibers of the invention also have a preferred tensile
modulus of about 300 g/denier or more, more preferably about 400
g/denier or more, more preferably about 500 g/denier or more, more
preferably about 1,000 g/denier or more and most preferably about
1,500 g/denier or more. The fibers of the invention also have a
preferred energy-to-break of about 15 J/g or more, more preferably
about 25 J/g or more, more preferably about 30 J/g or more and most
preferably have an energy-to-break of about 40 J/g or more.
These combined high strength properties are obtainable by employing
well known processes. U.S. Pat. Nos. 4,413,110, 4,440,711,
4,535,027, 4,457,985, 4,623,547 4,650,710 and 4,748,064 generally
discuss the formation of preferred high strength, extended chain
polyethylene fibers employed in the present invention. Such
methods, including solution grown or gel fiber processes, are well
known in the art. Methods of forming each of the other preferred
fiber types, including para-aramid fibers, are also conventionally
known in the art, and the fibers are commercially available.
As stated above, each of fibrous layers 20, 22, 24 and 26 further
comprise a polymeric binder material, which is also commonly
referred to in the art as a polymeric matrix material. The
polymeric matrix material includes one or more components and
facilitates the consolidation, or merging together, of multiple
fiber plies (i.e. multiple unitapes) when subjected to heat and/or
pressure, thereby forming a consolidated, unitary, single-layer
element. For each of fibrous layers 20, 22, 24 and 26, polymeric
binder material coated on their component fibers comprises a
material that is resistant to dissolution by water and resistant to
dissolution by one or more organic solvents is optional. The
surfaces of each of the fibers forming said fibrous layers are at
least partially coated with a polymeric matrix material, and are
preferably substantially coated to by the matrix material. Coating
the fibers of woven fibrous layers or fabrics with the polymeric
matrix material may be conducted either before or after weaving.
Said fibrous layers may alternately comprise a plurality of yarn
plies that are coated with a matrix material and consolidated, or
felted structures comprising fibers in a random orientation
embedded in a suitable matrix material that are matted and
compressed together.
The fibrous layers of the invention may be prepared using a variety
of matrix materials, including both low modulus, elastomeric matrix
materials and high modulus, rigid matrix materials. Useful
polymeric matrix materials include both low modulus, thermoplastic
matrix materials and high modulus, thermosetting matrix materials
having the above desired properties, or a combination thereof.
Suitable thermoplastic matrix materials preferably have an initial
tensile modulus of less than about 6,000 psi (41.3 MPa), and
suitable high modulus, thermosetting materials preferably have an
initial tensile modulus of at least about 300,000 psi (2068 MPa),
each as measured at 37.degree. C. by ASTM D638. As used herein
throughout, the term tensile modulus means the modulus of
elasticity as measured by ASTM D638 for a matrix material. For the
manufacture of soft body armor, low modulus thermoplastic matrix
materials are most preferred. Preferred low modulus thermoplastic
materials have a tensile modulus of about 4,000 psi (27.6 MPa) or
less, more preferably about 2400 psi (16.5 MPa) or less, more
preferably 1200 psi (8.23 MPa) or less, and most preferably is
about 500 psi (3.45 MPa) or less.
As described herein, the polymeric matrix material is independently
resistant to dissolution by, particularly sea water, and
independently resistant to dissolution by one or more organic
solvents, such as diesel or non-diesel gasoline, gun lube,
petroleum and organic solvents derived from petroleum. The
polymeric matrix material is also preferably resistant to
dissolution by a combination of water and one or more organic
solvents. Conventionally, there are two types of polymers which are
predominantly used in the manufacture of soft body armor, i.e.
solvent-based and water-based synthetic rubbers; and polyurethane
(typically water-based). Such synthetic rubbers are generally block
copolymers of styrene and isoprene, particularly
styrene-isoprene-styrene (SIS) copolymers. These SIS copolymers are
processed in both solvent-based solutions and water-based
dispersions. Solvent-based synthetic rubbers are generally
sensitive to petroleum solvents and will dissolve upon exposure.
Such solvent-based synthetic rubbers are generally unaffected by
water. However, water-based dispersions can be very sensitive to
water and sea water, depending on the method and materials of
dispersion. Currently employed polyurethane matrix polymers, due to
their inherent polarity, are generally resistant to petroleum
solvents, with some exceptions. Water-based polyurethanes can be
degraded by water, particularly sea water, which can cause a
hydrolytic breakdown of the polyurethane chain, resulting in a
reduction in both molecular weight and physical properties.
It has been found that polymers which are both polar and
hydrolytically stable achieve the desired balance of water
resistance and organic solvent resistance, while maintaining the
desired ballistic resistance properties necessary for an effective
ballistic resistant article. Polar polymers are generally resistant
to dissolution by non-polar organic solvents, and hydrolytically
stable polymers are stable to hydrolysis by water, i.e. resistant
to chemical decomposition when exposed to water. Accordingly,
ballistic resistant articles formed incorporating such polymeric
matrix materials retain their ballistic resistance properties after
prolonged exposure to such liquids.
In the preferred embodiments of the invention, suitable polymeric
matrix materials preferably include synthetic rubbers, diene
rubbers and styrenic block copolymers including
styrene-isoprene-styrene (SIS) and styrene-butadiene-styrene (SBS),
polar vinyl-based polymers, polar acrylic polymers, polyvinyl
chloride homopolymer, polyvinyl chloride copolymer, polyvinyl
chloride terpolymer, polyvinyl butyral, polyvinylidene chloride,
polyvinylidene fluoride polar ethylene vinyl acetate copolymers,
polar ethylene acrylic acid copolymers, silicone, thermoplastic
polyurethanes, nitrile rubber, polychloroprenes such as Neoprene
(manufactured by DuPont), polycarbonates, polyketones, polyamides,
cellulosics, polyimides, polyesters, epoxies, alkyds, phenolics,
polyacrylonitrile, polyether sulfones and combinations thereof.
Also suitable are other polar, hydrolytically stable polymers not
specified herein. Non-polar synthetic rubbers and styrenic block
copolymers, such as SIS and SBS, generally should be modified with
polar groups, such as by the grafting of carboxyl groups or adding
acid or alcohol functionality, or any other polar group, to be
sufficiently oil repellant. For example, non-polar polymers may be
copolymerized with monomers containing carboxylic acid groups such
as acrylic acid or maleic acid, or another polar group such as
amino, nitro or sulfonate groups. Such techniques are well known in
the art.
Particularly preferred are polar polymers which have a C--C polymer
backbone. As stated herein, polar polymers are generally resistant
to dissolution by non-polar organic solvents. Polymers having a
C--C-- backbone, such as vinyl-based polymers including, for
example, acrylics, ethylene vinyl acetate, polyvinylidene chloride,
etc., have a hydrolytically stable molecular structure. Also
particularly preferred are polar, thermoplastic polyurethanes,
particularly those that have been formulated to enhance hydrolytic
stability. Unlike C--C linkages, urethane linkages and ester
linkages are generally susceptible hydrolytic degradation.
Accordingly, polymers having such linkages generally are formulated
or modified to enhance water repellency and hydrolytic stability.
For example, polyurethanes may be formulated to enhance hydrolytic
stability through copolymerization with polyether polyol or
aliphatic polyol components, or other components known to enhance
hydrolytic stability. The main polyurethane producing reaction is
between an aliphatic or aromatic diisocyanate and a polyol,
typically a polyethylene glycol or polyester polyol, in the
presence of catalysts. Selection of the isocyanate co-reactant can
also influence the hydrolytic stability. Bulky pendant groups on
either or both of the co-reactants can also protect the urethane
linkage from attack. Polyurethane can be made in a variety of
densities and hardnesses by varying the type of monomers used and
by adding other substances to modify their characteristics or
enhance their hydrolytic stability, such as with water repellants,
pH buffers, cross-linking agents and chelating agents, etc. The
most preferred polyurethane matrix material comprises a polar,
hydrolytically stable, polyether- or aliphatic-based thermoplastic
polyurethane, which are preferred over polyester-based
polyurethanes.
The thermoplastic polyurethane may be a homopolymer, a copolymer,
or a blend of a polyurethane homopolymer and a polyurethane
copolymer. Such polymers are commercially available. Such
polyurethanes are generally available as aqueous solutions,
dispersions or emulsions, in which the solids component may range
from about 20% to 80% by weight, more preferably from about 40% to
about 60% by weight, with the remaining weight being water. An
aqueous system is preferred for ease of use. Preferred polyurethane
coated fibrous layers are described in U.S. patent application Ser.
No. 11/213,253, which is incorporated herein by reference in its
entirety.
The glass transition temperature (Tg) of the preferred
thermoplastic matrix materials is preferably less than about
0.degree. C., more preferably the less than about -40.degree. C.,
and most preferably less than about -50.degree. C. Preferred
thermoplastic materials also have a preferred elongation to break
of at least about 50%, more preferably at least about 100% and most
preferably an elongation to break of at least about 300%.
With regard to the woven fibrous layers, it is generally not
necessary for the fibers to be coated with the polymeric matrix
material, because no consolidation is conducted. However, it is
preferred that the fibers comprising the woven fibrous layers be
coated with a polymeric matrix material that is resistant to
dissolution by water, and resistant to dissolution by one or more
organic solvents, to achieve the benefits described herein.
The rigidity, impact and ballistic properties of the articles
formed from the fabric composites of the invention are effected by
the tensile modulus of the matrix polymer. For example, U.S. Pat.
No. 4,623,574 discloses that fiber reinforced composites
constructed with elastomeric matrices having tensile moduli less
than about 6000 psi (41,300 kPa) have superior ballistic properties
compared both to composites constructed with higher modulus
polymers, and also compared to the same fiber structure without a
matrix. However, low tensile modulus matrix polymers also yield
lower rigidity composites. Further, in certain applications,
particularly those where a composite must function in both
anti-ballistic and structural modes, there is needed a superior
combination of ballistic resistance and rigidity. Accordingly, the
most appropriate type of matrix polymer to be used will vary
depending on the type of article to be formed from the fabrics of
the invention. In order to achieve a compromise in both properties,
a suitable matrix material may combine both low modulus and high
modulus materials to form a single matrix material. The matrix
material may also include fillers such as carbon black or silica,
may be extended with oils, or may be vulcanized by sulfur,
peroxide, metal oxide or radiation cure systems as is well known in
the art.
The application of the matrix is conducted prior to consolidating
the fiber plies. The matrix may be applied to a fiber in a variety
of ways, and the term "coated" is not intended to limit the method
by which the matrix material is applied onto the fiber surface or
surfaces. For instance, the polymeric matrix material may be
applied in solution form by spraying or roll coating a solution of
the matrix material onto fiber surfaces, wherein a portion of the
solution comprises the desired polymer or polymers and a portion of
the solution comprises a solvent capable of dissolving the polymer
or polymers, followed by drying.
Another method is to apply a neat polymer of the coating material
to fibers either as a liquid, a sticky solid or particles in
suspension or as a fluidized bed. Alternatively, the coating may be
applied as a solution or emulsion in a suitable solvent which does
not adversely affect the properties of the fiber at the temperature
of application. For example, the fiber can be transported through a
solution of the matrix material to substantially coat the fiber and
then dried to form a coated fiber. The resulting coated fiber can
then be arranged into the desired fibrous layer configuration. In
another coating technique, a layer of fibers may first be arranged,
followed by dipping the layer into a bath of a solution containing
the matrix material dissolved in a suitable solvent, such that each
individual fiber is substantially coated with the matrix material,
and then dried through evaporation of the solvent. The dipping
procedure may be repeated several times as required to place a
desired amount of matrix material coating on the fibers, preferably
encapsulating each of the individual fibers or covering 100% of the
fiber surface area with the matrix material.
While any liquid capable of dissolving or dispersing a polymer may
be used, preferred groups of solvents include water, paraffin oils
and aromatic solvents or hydrocarbon solvents, with illustrative
specific solvents including paraffin oil, xylene, toluene, octane,
cyclohexane, methyl ethyl ketone (MEK) and acetone. The techniques
used to dissolve or disperse the coating polymers in the solvents
will be those conventionally used for the coating of similar
materials on a variety of substrates.
Other techniques for applying the coating to the fibers may be
used, including coating of the high modulus precursor (gel fiber)
before the fibers are subjected to a high temperature stretching
operation, either before or after removal of the solvent from the
fiber (if using the gel-spinning fiber forming technique). The
fiber may then be stretched at elevated temperatures to produce the
coated fibers. The gel fiber may be passed through a solution of
the appropriate coating polymer under conditions to attain the
desired coating. Crystallization of the high molecular weight
polymer in the gel fiber may or may not have taken place before the
fiber passes into the solution. Alternatively, the fiber may be
extruded into a fluidized bed of an appropriate polymeric powder.
Furthermore, if a stretching operation or other manipulative
process, e.g. solvent exchanging, drying or the like is conducted,
the coating may be applied to a precursor material of the final
fiber. In the most preferred embodiment of the invention, the
fibers of the invention are first coated with the matrix material,
followed by arranging a plurality of fibers into either a woven or
non-woven fiber layer. Such techniques are well known in the
art.
Accordingly, the fibers of the invention may be coated on,
impregnated with, embedded in, or otherwise applied with a matrix
material by applying the matrix material to the fibers and then
consolidating the matrix material-fibers combination to form a
composite. As stated above, by "consolidating" it is meant that the
matrix material and each individual fiber layer are combined into a
single unitary layer. Consolidation can occur via drying, cooling,
heating, pressure or a combination thereof. The term "composite"
refers to consolidated combinations of fibers with the matrix
material. As discussed previously, the term "matrix" as used herein
is well known in the art, and is used to represent a binder
material, such as a polymeric binder material, that binds the
fibers together after consolidation.
As illustrated in FIGS. 1 and 2, polymer films 14, 16 and 18 are
attached to each surface of fibrous layers 20, 22, 24 and 26. As
illustrated in FIG. 2, the polymer films 14, 16 and 18 are
preferably attached to said fibrous layers after any applicable
consolidation steps. Suitable polymers for said polymer films
non-exclusively include thermoplastic and thermosetting polymers.
Suitable thermoplastic polymers non-exclusively may be selected
from the group consisting of polyolefins, polyamides, polyesters,
polyurethanes, vinyl polymers, fluoropolymers and co-polymers and
mixtures thereof. Of these, polyolefin layers are preferred. The
preferred polyolefin is a polyethylene. Non-limiting examples of
polyethylene films are low density polyethylene (LDPE), linear low
density polyethylene (LLDPE), linear medium density polyethylene
(LMDPE), linear very-low density polyethylene (VLDPE), linear
ultra-low density polyethylene (ULDPE), high density polyethylene
(HDPE). Of these, the most preferred polyethylene is LLDPE.
Suitable thermosetting polymers non-exclusively include thermoset
allyls, aminos, cyanates, epoxies, phenolics, unsaturated
polyesters, bismaleimides, rigid polyurethanes, silicones, vinyl
esters and their copolymers and blends, such as those described in
U.S. Pat. Nos. 6,846,758, 6,841,492 and 6,642,159. In each
embodiment, polymer films 14, 16 and 18 may be the same or
different.
Polymer films 14, 16 and 18 are preferably extruded layers that are
cooled and attached to the fibrous layers by lamination using well
known lamination techniques. Typically, laminating is done by
positioning the individual layers on one another under conditions
of sufficient heat and pressure to cause the layers to combine. The
individual layers are positioned on one another, and the
combination is then typically passed through the nip of a pair of
heated laminating rollers by techniques well known in the art.
Lamination heating may be done at temperatures ranging from about
95.degree. C. to about 175.degree. C., preferably from about
105.degree. C. to about 175.degree. C., at pressures ranging from
about 5 psig (0.034 MPa) to about 100 psig (0.69 MPa), for from
about 5 seconds to about 36 hours, preferably from about 30 seconds
to about 24 hours. In the embodiment of the invention where first
fibrous layer 20 and second fibrous layer 22 each consist of only a
single ply of fibers, the attachment of the polymer films to the
fibrous layers 20 and 22 and the attachment of the fibrous layers
20 and 22 to each other are preferably done in a single
lamination-consolidation step. Alternatively, the polymer films can
be attached to the fibers in the coating step where the binder
resin is either applied to the fibers and then laid onto the film,
or applied to the film and the fibers laid into the resin on a
substrate and allowed to dry while in contact with one another. In
the embodiment of the invention where first fibrous layer 24 and
second fibrous layer 26 comprise a plurality of non-woven fiber
plies, it is preferable that said fibrous layers are consolidated
prior to lamination of the polymer films 14, 16 and 18.
Suitable consolidation conditions for consolidating fiber plies
into a fibrous layer 24 and/or 26 are similar to said lamination
conditions. In a typical consolidation process, the cross-plied
fiber plies are pressed together at a temperature of from about
200.degree. F. (.about.93.degree. C.) to about 350.degree. F.
(.about.177.degree. C.), more preferably at a temperature of from
about 200.degree. F. to about 300.degree. F. (.about.149.degree.
C.) and most preferably at a temperature of from about 200.degree.
F. to about 250.degree. F. (.about.121.degree. C.), and at a
pressure of from about 25 psi (.about.172 kPa) to about 500 psi
(3447 kPa) or higher, for a duration of about 30 seconds to about
24 hours. Such methods are conventionally known in the art. When
heating, it is possible that the matrix can be caused to stick or
flow without completely melting. However, generally, if the matrix
material is caused to melt, relatively little pressure is required
to form the composite, while if the matrix material is only heated
to a sticking point, more pressure is typically required. The
consolidation step may generally take from about 10 seconds to
about 24 hours. Similar to molding, suitable consolidation
temperatures, pressures and times are generally dependent on the
type of polymer, polymer content, process used and type of fiber.
The consolidation may alternately be conducted in an autoclave, as
is conventionally known in the art. The consolidation of the fiber
plies into a fibrous layer 24 and/or 26 and the attachment of the
polymer films may also be done in a single consolidation step.
Structures 10 and 12 of the invention may also be formed by
combining the multiple component layers of each structure by
molding under heat and pressure in a suitable molding apparatus.
Generally, molding is conducted at a pressure of from about 50 psi
(344.7 kPa) to about 5000 psi (34474 kPa), more preferably about
100 psi (689.5 kPa) to about 1500 psi (10342 kPa), most preferably
from about 150 psi (1034 kPa) to about 1000 psi (6895 kPa). Higher
pressures of from about 500 psi (3447 kPa) to about 5000 psi, more
preferably from about 750 psi (5171 kPa) to about 5000 psi and more
preferably from about 1000 psi to about 5000 psi may also be
utilized. The molding step may take from about 4 seconds to about
45 minutes. Preferred molding temperatures range from about
200.degree. F. (.about.93.degree. C.) to about 350.degree. F.
(.about.177.degree. C.), more preferably at a temperature from
about 200.degree. F. to about 300.degree. F. (.about.149.degree.
C.) and most preferably at a temperature from about 200.degree. F.
to about 280.degree. F. (.about.138.degree. C.). Suitable molding
temperatures, pressures and times will generally vary depending on
the type of polymer matrix type, polymer matrix content, number of
layers, mass of material and type of fiber. While each of the
molding and consolidation techniques described herein are similar,
each process is different. Particularly, molding is a batch process
and consolidation is a continuous process. Further, molding
typically involves the use of a mold, such as a shaped mold or a
match-die mold. The pressure under which the fabrics of the
invention are molded has a direct effect on the stiffness of the
resulting molded product. Particularly, the higher the pressure at
which the composites are molded, the higher the stiffness, and
vice-versa. In addition to the molding pressure, the quantity,
thickness and composition of the fabric layers, matrix type and
polymer film type also directly affects the stiffness of the
articles formed from the inventive composites.
The composite structures 10 and 12 of the invention may optionally
be calendared under heat and pressure to smooth or polish their
surfaces. Calendaring methods are well known in the art and may be
conducted prior to or after molding.
In the preferred embodiment of the invention, the polymer film
layers preferably comprise from about 2% to about 20% by weight of
the overall fibrous composite material (which includes the weight,
of the fibers, the optional polymeric matrix material, and the
polymer films), more preferably from about 2% to about 15% by
weight and most preferably from about 2% to about 10% by weight of
the overall fibrous composite material. The percent by weight of
the polymer film layers will generally vary depending on the number
of fabric layers forming the multilayered film. If present, the
proportion of the matrix material making up a fibrous layer
preferably comprises from about 3% to about 30% by weight of the
layer, more preferably from about 3% to about 20% by weight of the
layer, more preferably from about 3% to about 16%, more preferably
from about 5% to about 15% and more preferably from about 11% to
about 15% by weight of the layer. The proportion of fibers making
up each fibrous layer of the invention preferably comprises from
about 60% to about 98% by weight of the layer, more preferably from
about 70% to about 95% by weight of the layer, and most preferably
from about 80% to about 90% by weight of the layer.
The thickness of the individual fibrous layers will correspond to
the thickness of the individual fibers and to the number of plies
forming a fibrous layer. Accordingly, a preferred single-ply
non-woven fibrous ply will have a preferred thickness of from about
5 .mu.m to about 3000 .mu.m, more preferably from about 15 .mu.m to
about 300 .mu.m and most preferably from about 25 .mu.m to about
125 .mu.m. A preferred single-layer, multi-ply, consolidated
non-woven fibrous layer will have a preferred thickness of from
about 12 .mu.m to about 3000 .mu.m, more preferably from about 15
.mu.m to about 385 .mu.m and most preferably from about 25 .mu.m to
about 255 .mu.m. A preferred woven fibrous layer will have a
preferred thickness of from about 25 .mu.m to about 500 .mu.m, more
preferably from about 75 .mu.m to about 385 .mu.m and most
preferably from about 125 .mu.m to about 255 .mu.m. The polymer
films are preferably very thin, having preferred thicknesses of
from about 1 .mu.m to about 250 .mu.m, more preferably from about 5
.mu.m to about 25 .mu.m and most preferably from about 5 .mu.m to
about 9 .mu.m. Structures 10 and 12 each have a preferred total
thickness of about 5 .mu.m to about 1000 .mu.m, more preferably
from about 6 .mu.m to about 750 .mu.m and most preferably from
about 7 .mu.m to about 500 .mu.m. While such thicknesses are
preferred, it is to be understood that other film thicknesses may
be produced to satisfy a particular need and yet fall within the
scope of the present invention. The articles of the invention
further have a preferred areal density of from about 0.25
lb/ft.sup.2 (psf) (1.22 kg/m.sup.2 (ksm)) to about 5.0 psf (24.41
ksm), more preferably from about 0.5 psf (2.44 ksm) to about 2.0
psf (9.76 ksm), more preferably from about 0.7 psf (3.41 ksm) to
about 1.5 psf (7.32 ksm), and most preferably from about 0.75 psf
(3.66 ksm) to about 1.25 psf (6.1 ksm).
The structures of the invention may be used in various applications
to form a variety of different ballistic resistant articles using
well known techniques. For example, suitable techniques for forming
ballistic resistant articles are described in, for example, U.S.
Pat. Nos. 4,623,574, 4,650,710, 4,748,064, 5,552,208, 5,587,230,
6,642,159, 6,841,492 and 6,846,758.
The structures are particularly useful for the formation of
flexible, soft armor articles, including garments such as vests,
pants, hats, or other articles of clothing, and covers or blankets,
used by military personnel to defeat a number of ballistic threats,
such as 9 mm full metal jacket (FMJ) bullets and a variety of
fragments generated due to explosion of hand-grenades, artillery
shells, Improvised Explosive Devices (IED) and other such devises
encountered in a military and peace keeping missions. As used
herein, "soft" or "flexible" armor is armor that does not retain
its shape when subjected to a significant amount of stress and is
incapable of being free-standing without collapsing. The structures
are also useful for the formation of rigid, hard armor articles. By
"hard" armor is meant an article, such as helmets, panels for
military vehicles, or protective shields, which have sufficient
mechanical strength so that it maintains structural rigidity when
subjected to a significant amount of stress and is capable of being
freestanding without collapsing. The structures can be cut into a
plurality of discrete sheets and stacked for formation into an
article or they can be formed into a precursor which is
subsequently used to form an article. Such techniques are well
known in the art.
Garments of the invention may be formed through methods
conventionally known in the art. Preferably, a garment may be
formed by adjoining the ballistic resistant articles of the
invention with an article of clothing. For example, a vest may
comprise a generic fabric vest that is adjoined with the ballistic
resistant structures of the invention, whereby the inventive
structures are inserted into strategically placed pockets. This
allows for the maximization of ballistic protection, while
minimizing the weight of the vest. As used herein, the terms
"adjoining" or "adjoined" are intended to include attaching, such
as by sewing or adhering and the like, as well as un-attached
coupling or juxtaposition with another fabric, such that the
ballistic resistant articles may optionally be easily removable
from the vest or other article of clothing. Articles used in
forming flexible structures like flexible sheets, vests and other
garments are preferably formed from using a low tensile modulus
matrix material. Hard articles like helmets and armor are
preferably formed using a high tensile modulus matrix material.
The ballistic resistance properties are determined using standard
testing procedures that are well known in the art. Particularly,
the protective power or penetration resistance of a structure is
normally expressed by citing the impacting velocity at which 50% of
the projectiles penetrate the composite while 50% are stopped by
the shield, also known as the V.sub.50 ballistic limit value. As
used herein, the "penetration resistance" of an article is the
resistance to penetration by a designated threat, such as physical
objects including bullets, fragments, shrapnel and the like, and
non-physical objects, such as a blast from explosion. For
composites of equal areal density, which is the weight of the
composite divided by the surface area, the higher the V.sub.50, the
better the resistance of the composite. The ballistic resistant
properties of the articles of the invention will vary depending on
many factors, particularly the type of fibers used to manufacture
the fabrics. However, the use of a polymeric matrix material that
is resistant to dissolution by water, and resistant to dissolution
by one or more organic solvents does not negatively affect the
ballistic properties of the articles of the invention. The flexible
ballistic armor, weighing at least about 0.75 psf, formed herein
have a V.sub.50 of at-least 1450 fps (442 mps) when impacted with
17 grain Fragment Simulating Projectile (FSP) projectile or 9 mm
Full Metal Jacket (FMJ) hand gun bullet. The flexible ballistic
armor of this invention is also preferably characterized in
retaining at least about 85%, more preferably at least 90% of
V.sub.50 performance after immersion in tap water or sea water when
impacted with a 17 grain FSP or 9 mm FMJ hand gun bullet. Under
these conditions, the flexible ballistic armor also exhibits a
weight increase of preferably not more than 50%, and more
preferably not more than about 40% from its dry weight. Moreover,
the flexible ballistic armor of this invention preferably is
characterized in retaining at least about 85%, more preferably at
least about 90%, of its V.sub.50 performance after immersion in
gasoline at 70.degree. F..+-.5.degree. F. (21.degree.
C..+-.2.8.degree. C.) for 4 hours, when impacted with a 9 mm FMJ
bullet or a 17 grain FSP.
The following examples serve to illustrate the invention:
EXAMPLE 1
Comparative
A ballistic shoot pack including 27 fabric layers was prepared for
testing of fragment resistance. Prior to forming the shoot pack,
the fabric layers were cut from a continuous laminated sheet of
material that comprised two consolidated plies of unidirectional,
high modulus polyethylene (HMPE) fibers impregnated with a
polymeric binder material comprising Kraton.RTM. D1107
thermoplastic binder resin. The HMPE fibers were SPECTRA.RTM. 1300
manufactured by Honeywell International Inc. and had a tenacity of
35 g/denier, a tensile modulus of 1150 g/denier and an elongation
at break of 3.4% The Kraton.RTM. D1107 resin is a
polystyrene-polyisoprene-polystrene-block copolymer comprising 14%
by weight styrene and is commercially available from Kraton
Polymers of Houston, Tex. Each fabric layer comprised 79.5% by
weight of fiber based on the weight the fibers plus the weight of
the binder resin, and comprised 20.5% by weight of binder resin
based on the weight of the fibers plus the weight of the binder
resin.
The two fiber plies of each layer were cross-plied such that the
fibers of one ply were oriented at a right angle to the fibers of
the second ply relative to the longitudinal fiber direction of each
fiber ply (conventional 0.degree./90.degree. configuration). The
plies were laminated between two linear low density polyethylene
(LLDPE) films, each having a thickness of 9 .mu.m and an areal
density of 16 gram/m.sup.2 (gsm). This construction is also known
in the art as SPECTRA SHIELD.RTM. LCR, commercially available from
Honeywell International, Inc. The lamination process included
pressing the LLDPE films onto the cross-plied material at
110.degree. C., under 200 psi (1379 kPa) pressure for 30 minutes,
thereby forming a continuous laminated sheet of material having a
thickness of 0.06'' (1.524 mm). The sheet was cut to form 27
separate layers, each having a length and width of 18''.times.18''
(45.7 mm.times.45.7 mm), and the total areal density of one fabric
layer was 150 gsm. The 27 layers were then loosely stacked together
to form the shoot pack. The layers were not bonded to each other.
The areal density of the shoot pack was 0.84 psf (4.01 ksm).
For testing against fragment resistance, the shoot pack was mounted
on a test frame and firmly clamped at the top of the frame. The
frame was mounted at a 90-degree orientation to the line of
fragment fired from a firmly mounted universal receiver. A 17 grain
Fragment Simulating Projectile was used for testing and conformed
to the shape, size and weight as per the MIL-P-46593A. V.sub.50
ballistic testing was conducted in accordance with the procedures
of MIL-STD-662E to experimentally determine the velocity at which a
bullet has a 50 percent chance of penetrating the test object.
Several 17 grain FSP fragments were fired, changing the velocity of
each fragment. The velocity of each fragment was moved down and up
depending whether the previous fragment shot was a complete
penetration or partially penetrated a few layers of the shoot pack.
An average velocity was achieved by including a minimum of four
partial penetrations and four complete fragment penetrations within
a velocity spread of 125 fps (38.1 mps). The average velocity of
the eight partial and complete penetrations was calculated and
called V.sub.50. The V.sub.50 of this shoot pack was calculated as
1500 fps (457.2 mps). The Specific Energy Absorption of the Target
(SEAT) was calculated as 27.86 J-m.sup.2/kg. A summary of the shoot
pack structure and the test results are shown in Table 1.
EXAMPLE 2
Comparative
A ballistic shoot pack was prepared similar to Example 1 but
including 33 stacked fabric layers. The areal density of the shoot
pack was 1.00 psf (4.88 ksm). The pack was tested for fragment
resistance as in Example 1. The V.sub.50 of this shoot pack was
calculated as 1705 fps (519.7 mps). The SEAT was calculated as
30.23 J-m.sup.2/kg. A summary of the shoot pack structure and the
test results are shown in Table 1.
EXAMPLE 3
Comparative
A ballistic shoot pack was prepared similar to Example 1 but
including 28 fabric layers. Also, in this example each fabric layer
comprised 89.9% by weight of fiber based on the weight of the
fibers plus the weight of the binder resin, and comprised 10.1% by
weight of the binder resin based on the weight of the fibers plus
the weight of the binder resin. The areal density of the shoot pack
was 0.76 psf (3.71 kg/m.sup.2). The pack was testing for fragment
resistance as in Example 1. The V.sub.50 of this shoot pack was
calculated as 1616 fps (492.6 mps). The SEAT was calculated as 35.7
J-m.sup.2/kg. A summary of the shoot pack structure and the test
results are shown in Table 1.
EXAMPLE 4
A ballistic shoot pack including 11 fabric layers was prepared for
testing of fragment resistance. The fabric layers were cut from a
continuous laminated sheet of material that was formed having the
structure illustrated in FIG. 2. Specifically, the material had the
following construction: a) a first LLDPE film; b) four plies of
unidirectional aramid fibers (1000 denier TWARON.RTM. fibers), said
plies oriented at 0.degree.,90.degree.,0.degree.,90.degree.
orientation; c) a second LLDPE film; d) four additional plies of
unidirectional aramid fibers, said plies oriented at
0.degree.,90.degree.,0.degree.,90.degree. orientation; and e) a
third LLDPE film.
The aramid fiber plies were coated with a water-based polyurethane
thermoplastic binder material (Bayer DISPERCOLL.RTM. U53
polyurethane resin) and the plies were consolidated with the binder
to form a monolithic non-woven fabric. The LLDPE films each had a
thickness of 9 .mu.m and an areal density of 16 gsm. Each fabric
layer comprised 86% by weight of aramid fiber based on the weight
of the fibers plus the weight of the binder resin, and comprised
14.0% by weight of binder resin based on the weight of the fibers
plus the weight of the binder resin. This multi-ply material was
laminated together at 110.degree. C. under 200 psi (1379 kPa)
pressure for 30 minutes forming a continuous fabric sheet having a
thickness of 0.021 (0.533 mm). The sheet was cut to form 11
separate layers, each having a length and width of 18''.times.18'',
and the total areal density of one fabric layer was 459 gsm. The 11
layers were then loosely stacked together to form the shoot pack.
The layers were not bonded to each other. The areal density of the
shoot pack was 1.01 psf (4.94 ksm). The shoot pack was tested for
fragment resistance as in Example 1. The V.sub.50 of this shoot
pack was calculated as 1841 fps (561.28). The SEAT was calculated
as 34.89 J-m.sup.2/kg. A summary of the shoot pack structure and
the test results are shown in Table 1.
TABLE-US-00001 TABLE 1 Layers Areal 17 grain per Density FSP,
V.sub.50 SEAT Resin shoot psf fps (J-m.sup.2/ Ex. Construction
Content pack (ksm) (mps) kg) 1 SPECTRA 20.5% 27 0.84 1500 27.86
SHIELD .RTM. LCR (4.10) (457.2) 2 SPECTRA 20.5% 33 1.00 1705 30.23
SHIELD .RTM. LCR (4.88) (519.7) 3 SPECTRA 10.1% 28 0.76 1616 35.70
SHIELD .RTM. LCR (3.71) (492.6) 4 LLDPE film/ 16% 11 1.01 1841
34.89 non-woven plies/ (4.94) (561.28) LLDPE film/ non-woven plies/
LLDPE film
EXAMPLE 5
Comparative
Example 1 was repeated, only the shoot pack included 25 fabric
layers and was tested against a 9 mm Full Metal Jacket bullet
(bullet weight: 124 grain). The size of the shoot pack was
18''.times.18'' (45.7 mm.times.45.7 mm). The areal density of the
shoot pack was 0.78 psf (3.81 ksm). For testing against 9 mm FMJ
bullet resistance, the shoot pack was mounted on a test frame
filled with Plastilina #1 clay and strapped on the frame. The
Plastilina filled frame was mounted at a 90-degree orientation to
the line of fragment fired from a firmly mounted universal
receiver. The 9 mm FMJ bullet used for testing confirmed the shape,
size and weight as per the National Institute of Justice (NIJ)
0101.04 test standard.
Ballistic testing was conducted in accordance with the procedures
of MIL-STD-662E. Several 9 mm FMJ bullets were fired, changing the
velocity of each one. The velocity of each bullet was moved down
and up depending whether the previous bullet shot was a complete
penetration or partially penetrated a few layers of the shoot pack.
An average velocity was achieved by including a minimum of four
partial penetrations and four complete fragment penetrations within
a velocity spread of 125 fps. The average of eight partial and
complete penetration velocities was calculated and called V.sub.50.
The V.sub.50 of this shoot pack was calculated as 1475 fps (449.6
mps) and the average backface deformation on Plastilina was
measured as 39 mm. The SEAT was calculated as 210.87 J-m.sup.2/kg.
A summary of the shoot pack structure and the test results are
shown in Table 2.
EXAMPLE 6
Comparative
A shoot pack as in Example 3 was tested against a 9 mm FMJ bullet
as in Example 5. The areal density of the shoot pack was 0.77 psf
(3.75 ksm). The V.sub.50 of this shoot pack was calculated as 1620
fps (493.8 mps) and the average backface deformation on Plastilina
was measured as 43 mm. The SEAT was calculated as 257.67
J-m.sup.2/kg. A summary of the shoot pack structure and the test
results are shown in Table 2.
EXAMPLE 7
Comparative
Example 6 was repeated with 9 mm FMJ bullet, but the resin content
of the fabric was dropped from 10.1% to 7.0%. The areal density of
the shoot pack was 0.77 psf (3.75 ksm). The V.sub.50 of this shoot
pack was calculated as 1571 fps (478.8 mps) and the average
backface deformation on Plastilina was measured as 55 mm. The SEAT
was calculated as 242.32 J-m.sup.2/kg. A summary of the shoot pack
structure and the test results are shown in Table 2.
EXAMPLE 8
A ballistic shoot pack was prepared by stacking 9 fabric layers of
material described in Example 4. The stacked layers were not bonded
to each other. The areal density of the shoot pack was 0.74 psf
(3.61 ksm). The shoot pack was tested for V.sub.50 against 9 mm FMJ
bullets as in Example 5. The V.sub.50 of this shoot pack was
calculated as 1572 fps (479 mps) and average backface deformation
on Plastilina was measured as 25 mm. The SEAT was calculated as
252.46 J-m.sup.2/kg. A summary of the shoot pack structure and the
test results are shown in Table 2.
TABLE-US-00002 TABLE 2 9 MM Layers Areal FMJ, per Density V.sub.50
Resin shoot psf fps Deformation SEAT Ex. Construction Content pack
(ksm) (mps) (mm) (J-m.sup.2/kg) 5 SPECTRA 20.5% 25 0.78 1475 39
210.87 SHIELD .RTM. LCR (3.81) (449.6) 6 SPECTRA 10.1% 28 0.77 1620
43 257.67 SHIELD .RTM. LCR (3.75) (493.8) 7 SPECTRA 7% 29 0.77 1571
55 242.32 SHIELD .RTM. LCR (3.75) (478.8) 8 LLDPE film/ 16% 9 0.74
1572 25 252.46 non-woven plies/ (3.61) (479) LLDPE film/ non-woven
plies/ LLDPE film
EXAMPLE 9
Comparative
A peel strength test was conducted as per ASTM D1876-01 on the
material described in Example 1. Ten 2-inch (5.08 cm).times.12-inch
(30.48 cm) sample strips were cut along either the 0.degree. or
90.degree. fiber direction from the fully laminated material sheet.
Each of these samples were gripped at the left and right edges of
one of the 2-inch wide ends in an INSTRON.RTM. testing machine,
leaving a central portion about 1-inch (2.54 cm) wide for peel
testing. This central portion of each sample was peeled at
90.degree. to determine the peel strength between the 0.degree. and
90.degree. plies for each sample. The average peel strength of the
ten samples was measured as 2.42 lbs. A summary of the material
structure and the test results are shown in Table 3.
EXAMPLE 10
Comparative
A peel strength test was conducted as per Example 9 on ten
2-inch.times.12-inch sample strips cut from the material described
in Example 3. The average peel strength of the ten samples was
measured as 1.01 lbs. A summary of the material structure and the
test results are shown in Table 3.
EXAMPLE 11
A peel strength test was conducted as per Example 9 on ten
2-inch.times.12-inch sample strips cut from the material described
in Example 4. The average peel strength of the ten samples was
measured as 2.62 lbs. A summary of the material structure and the
test results are shown in Table 3.
TABLE-US-00003 TABLE 3 Resin Peel Ex. Construction Content
Strength(lbs) 9 SPECTRA 20.5% 2.42 SHIELD .RTM. LCR 10 SPECTRA
10.1% 1.01 SHIELD .RTM. LCR 11 LLDPE film/ .sup. 16% 2.62 non-woven
plies/ LLDPE film/ non-woven plies/ LLDPE film
EXAMPLE 12
Comparative
The material of Example 1 was tested for water absorption per the
ASTM 570-05 testing method. Three test samples, each in the form of
a disk 2-inches (50.8 mm) in diameter, were soaked in a 4-inch
(50.8 mm) wide 8-inch (101.6 mm) long glass beaker filled with tap
water for 50 hours. A 1''.times.1''.times.0.2'' (25.4 mm.times.25.4
mm.times.5.1 mm) ceramic tile was placed on the samples so that
samples would not float in the water. Water absorption was recorded
at several time intervals by taking out one sample at a time from
the water, wiping them off with a dry cloth and weighing the
sample. A summary of the material structure and the test results
are shown in Table 4.
EXAMPLE 13
The material of Example 4 was tested for water absorption following
the same method used in Example 12. A summary of the material
structure and the test results are shown in Table 4. As shown in
the table, the water absorption rate of the material from Example
13 was lower than the absorption rate of the material from
comparative Example 12.
TABLE-US-00004 TABLE 4 0 10 30 Ex. Construction minutes minutes
minutes 1 hour 50 hours 12 SPECTRA Control 6.3% 6.7% 6.9% 17.2%
SHIELD .RTM. LCR 13 LLDPE film/ Control 3.1% 3.5% 3.9% 12.6%
non-woven plies/ LLDPE film/ non-woven plies/ LLDPE film
EXAMPLE 14
Comparative
The material of Example 1 was tested for gasoline absorption as per
the ASTM 570-05 guidelines. Similar to Examples 12 and 13, three
test samples, each in the form of a disk 2-inches (50.8 mm) in
diameter, were soaked in a 4-inch (50.8 mm) wide 8-inch (101.6 mm)
long glass beaker filled with gasoline instead of water for four
hours. A 1''.times.1''.times.0.2'' (25.4 mm.times.25.4 mm.times.5.1
mm) ceramic tile was placed on the samples so that samples would
not float in the gasoline. The effect of gasoline absorption was
recorded by visual inspection of the sample. A summary of the
material structure and the test results are shown in Table 5.
EXAMPLE 15
The material of Example 4 was tested for gasoline absorption
following the same method used in Example 14. The effect of
gasoline absorption was recorded by visual inspection of the
sample. A summary of the material structure and the test results
are shown in Table 5. As shown in the table, the samples in Example
14 showed separation of the fiber plies and the LDPE films in one
minute after soaking in gasoline. However, the material in Example
15 showed no affect after soaking in gasoline for 4 hours.
TABLE-US-00005 TABLE 5 0 30 Ex. Construction minutes 1 minute
minutes 1 hour 4 hours 14 SPECTRA Control Fiber N/A N/A N/A SHIELD
.RTM. LCR Plies and LDPE Films Separated 15 LLDPE film/ Control No
No No No non-woven plies/ Affect Affect Affect Affect LLDPE film/
non-woven plies/ LLDPE film
EXAMPLE 16
Comparative
The material of Example 1 was tested for salt water absorption per
the ASTM 570-05 testing method. Three test samples, each in the
form of a disk 2-inches (50.8 mm) in diameter, were soaked in a
4-inch (50.8 mm) wide 8-inch (101.6 mm) long glass beaker filled
with a salt water mixture (comparable to sea water) for 270 hours.
A 1''.times.1''.times.0.2'' (25.4 mm.times.25.4 mm.times.5.1 mm)
ceramic tile was placed on the samples so that samples would not
float in the water. Water absorption was recorded at several time
intervals by taking out one sample at a time from the water, wiping
them off with a dry cloth and weighing the sample. A summary of the
material structure and the test results are shown in Tables 6A and
6B.
EXAMPLE 17
The material of Example 4 was tested for water absorption following
the same method used in Example 16. A summary of the material
structure and the test results are shown in Tables 6A and 6B. As
shown in the table, the water absorption rate of the material from
Example 17 was lower than the absorption rate of the material from
comparative Example 16.
TABLE-US-00006 TABLE 6A Ex. Construction 0 minutes 10 minutes 30
minutes 1 hour 16 SPECTRA Control 4.32% 4.71% 5.09% SHIELD .RTM.
LCR 17 LLDPE film/ Control 1.50% 2.72% 3.16% non-woven plies/ LLDPE
film/ non-woven plies/ LLDPE film
TABLE-US-00007 TABLE 6B Ex. Construction 24 hours 150 hours 270
hours 16 SPECTRA 7.53% 9.79% 9.79% SHIELD .RTM. LCR 17 LLDPE film/
6.23% 6.23% 6.23% non-woven plies/ LLDPE film/ non-woven plies/
LLDPE film
EXAMPLE 18
A five-ply material was formed including two unidirectional plies
of TWARON.RTM. 1000 denier aramid fibers coated with a water-based
polyurethane thermoplastic binder material (Bayer DISPERCOLL.RTM.
U53) and three LLDPE films. The five-ply material was formed into a
structure as illustrated in FIG. 1, i.e. LLDPE film/0.degree.
unitape/LLDPE film/90.degree. unitape/LLDPE film. Each LLDPE film
had a thickness of 9 .mu.m and an areal density of 16 gsm. Each
unidirectional ply comprised 86% by weight of aramid fiber based on
the weight of the fibers plus the weight of the binder resin, and
comprised 14% by weight of binder resin. The five-ply material was
laminated together at 110.degree. C. under 200 psi (1379 kPa)
pressure for 30 minutes forming a monolithic continuous fabric
sheet having a thickness of 0.021 (0.533 mm). The sheet was cut to
form separate layers, each having a length and width of
18''.times.18'', and the total areal density of one fabric layer
was 116 gsm. Thirty-two separate layers were then loosely stacked
together to form a ballistic shoot pack. The layers were not bonded
to each other.
A dry shoot pack of this construction was subjected to ballistic
testing against a 9 mm FMJ bullet (bullet weight: 124 grain), as
described in Example 5, without prior soaking in water. A summary
of the shoot pack structure and the ballistic test results are
shown in Table 7.
EXAMPLE 19
A second shoot pack of this construction was soaked in sea water
for 24 hours, followed by 15 minutes of vertical drip-drying to
drain out any water trapped between the shoot pack layers. This
shoot pack was then subjected to ballistic testing against a 9 mm
FMJ bullet as in Example 18. A summary of the shoot pack structure
and the ballistic test results are shown in Table 7.
TABLE-US-00008 TABLE 7 Layers Areal per Density 9 MM Backface Resin
shoot psf FMJ V50 Trauma Ex. Condition Content pack (ksm) fps (mps)
(mm) 18 Control, dry 17% 32 0.76 1289 27 (3.71) (392.9) 19 Soaked
in 17% 32 1.00 959 27 Sea Water (4.88) (292.3) for 24 hours
EXAMPLE 20
The material of Example 18 was tested for water absorption as
described in Example 12. A summary of the test results are shown in
Table 8.
TABLE-US-00009 TABLE 8 0 10 30 1 24 Ex. minutes minutes minutes
hour hours 20 0 6.6% 6.8% 7.1% 15.6%
EXAMPLE 21
The material of Example 18 was tested for gasoline absorption as
described in Example 14. A summary of the test results are shown in
Table 9.
TABLE-US-00010 TABLE 9 0 1 30 1 4 Ex. minutes minute minutes hour
hours 21 No No No No No affect affect affect affect affect
While the present invention has been particularly shown and
described with reference to preferred embodiments, it will be
readily appreciated by those of ordinary skill in the art that
various changes and modifications may be made without departing
from the spirit and scope of the invention. It is intended that the
claims be interpreted to cover the disclosed embodiment, those
alternatives which have been discussed above and all equivalents
thereto.
* * * * *
References